CreateSalesOrderLineItem: auto-apply sales price based on part price_breaks, currency, and quantity (#10549)

* updated part api mixin and part serializer to include salepricebreaks when explicitly queried

* fixed bug in ApiForm that prevents form field value from updating correctly

* CreateSalesOrderLineItem form now automatically applies price break based on currency and quantity for a part

* bumped API version due to PartsList api price_breaks query param

* fixed incorrect field names

* Remove whitespace

* Increase database query limit from 20 to 25

* updated ApiForm to propagate false and 0 as values to their respective fields, updated ApiFormField to eagerly apply AdjustValue to apply adjustments when onChange does not fire (when the value does not truly change)

* updated pagination number check to a range instead of discreet values.

---------

Co-authored-by: Matthias Mair <code@mjmair.com>
Co-authored-by: Oliver <oliver.henry.walters@gmail.com>

src/backend/InvenTree/InvenTree/api_version.py

@@ -1,12 +1,15 @@
 """InvenTree API version information."""
 
 # InvenTree API version
-INVENTREE_API_VERSION = 411
+INVENTREE_API_VERSION = 412
 
 """Increment this API version number whenever there is a significant change to the API that any clients need to know about."""
 
 INVENTREE_API_TEXT = """
 
+v412 -> 2025-10-19 : https://github.com/inventree/InvenTree/pull/10549
+    - added a new query parameter for the PartsList api: price_breaks (default: false)
+
 v411 -> 2025-06-19 : https://github.com/inventree/InvenTree/pull/10630
     - Editorialy changes to machine api - no functional changes
 

src/backend/InvenTree/part/api.py

@@ -1022,6 +1022,9 @@ class PartMixin(SerializerContextMixin):
         if str2bool(self.request.query_params.get('parameters', False)):
             queryset = queryset.prefetch_related('parameters', 'parameters__template')
 
+        if str2bool(self.request.query_params.get('price_breaks', True)):
+            queryset = queryset.prefetch_related('salepricebreaks')
+
         return queryset
 
     def get_serializer(self, *args, **kwargs):
@@ -1061,6 +1064,7 @@ class PartOutputOptions(OutputConfiguration):
         InvenTreeOutputOption('category_detail'),
         InvenTreeOutputOption('location_detail'),
         InvenTreeOutputOption('path_detail'),
+        InvenTreeOutputOption('price_breaks'),
     ]
 
 

src/backend/InvenTree/part/serializers.py

@@ -213,10 +213,14 @@ class PartTestTemplateSerializer(
 
 @register_importer()
 class PartSalePriceSerializer(
-    DataImportExportSerializerMixin, InvenTree.serializers.InvenTreeModelSerializer
+    InvenTree.serializers.FilterableSerializerMixin,
+    DataImportExportSerializerMixin,
+    InvenTree.serializers.InvenTreeModelSerializer,
 ):
     """Serializer for sale prices for Part model."""
 
+    no_filters = True
+
     class Meta:
         """Metaclass defining serializer fields."""
 
@@ -692,6 +696,7 @@ class PartSerializer(
             'pricing_max',
             'pricing_updated',
             'responsible',
+            'price_breaks',
             # Annotated fields
             'allocated_to_build_orders',
             'allocated_to_sales_orders',
@@ -731,6 +736,7 @@ class PartSerializer(
         create = kwargs.pop('create', False)
         # pricing = kwargs.pop('pricing', True)
         # path_detail = kwargs.pop('path_detail', False)
+        # price_breaks = kwargs.pop('price_breaks', False)
 
         super().__init__(*args, **kwargs)
 
@@ -750,6 +756,9 @@ class PartSerializer(
         if not path_detail:
             self.fields.pop('category_path', None)
 
+        if not price_breaks:
+            self.fields.pop('price_breaks', None)
+
         if not pricing:
             self.fields.pop('pricing_min', None)
             self.fields.pop('pricing_max', None)
@@ -1032,6 +1041,12 @@ class PartSerializer(
         PartParameterSerializer(many=True, read_only=True, allow_null=True)
     )
 
+    price_breaks = enable_filter(
+        PartSalePriceSerializer(source='salepricebreaks', many=True, read_only=True),
+        False,
+        filter_name='price_breaks',
+    )
+
     # Extra fields used only for creation of a new Part instance
     duplicate = DuplicatePartSerializer(
         label=_('Duplicate Part'),

src/backend/InvenTree/part/test_api.py

@@ -32,6 +32,7 @@ from part.models import (
     PartParameter,
     PartParameterTemplate,
     PartRelated,
+    PartSellPriceBreak,
     PartTestTemplate,
 )
 from stock.models import StockItem, StockLocation
@@ -2059,8 +2060,8 @@ class PartListTests(PartAPITestBase):
             with CaptureQueriesContext(connection) as ctx:
                 self.get(url, query, expected_code=200)
 
-            # No more than 20 database queries
-            self.assertLess(len(ctx), 20)
+            # No more than 25 database queries
+            self.assertLess(len(ctx), 25)
 
         # Test 'category_detail' annotation
         for b in [False, True]:
@@ -2076,6 +2077,80 @@ class PartListTests(PartAPITestBase):
             # No more than 20 DB queries
             self.assertLessEqual(len(ctx), 20)
 
+    def test_price_breaks(self):
+        """Test that price_breaks parameter works correctly and efficiently."""
+        url = reverse('api-part-list')
+
+        # Create some parts with sale price breaks
+        for i in range(5):
+            part = Part.objects.create(
+                name=f'Part with breaks {i}',
+                description='A part with sale price breaks',
+                category=PartCategory.objects.first(),
+                salable=True,
+            )
+
+            # Create multiple price breaks for each part
+            for qty, price in [(1, 10 + i), (10, 9 + i), (100, 8 + i)]:
+                PartSellPriceBreak.objects.create(
+                    part=part, quantity=qty, price=price, price_currency='USD'
+                )
+
+        # Test 1: Without price_breaks parameter (default is False, field should not be included)
+        response = self.get(
+            url, {'limit': 5, 'search': 'Part with breaks'}, expected_code=200
+        )
+
+        self.assertEqual(len(response.data['results']), 5)
+        first_result = response.data['results'][0]
+        self.assertNotIn('price_breaks', first_result)
+
+        # Test 2: Explicitly with price_breaks=false
+        with CaptureQueriesContext(connection) as ctx:
+            response = self.get(
+                url,
+                {'limit': 5, 'price_breaks': False, 'search': 'Part with breaks'},
+                expected_code=200,
+            )
+
+        first_result = response.data['results'][0]
+        self.assertNotIn('price_breaks', first_result)
+
+        query_count_without_price_breaks = len(ctx)
+
+        # Test 3: Explicitly with price_breaks=true
+        with CaptureQueriesContext(connection) as ctx:
+            response = self.get(
+                url,
+                {'limit': 5, 'price_breaks': True, 'search': 'Part with breaks'},
+                expected_code=200,
+            )
+
+        # Should have price_breaks field with data
+        for result in response.data['results']:
+            self.assertIn('price_breaks', result)
+            self.assertIsInstance(result['price_breaks'], list)
+            self.assertEqual(len(result['price_breaks']), 3)
+
+            for pb in result['price_breaks']:
+                self.assertIn('pk', pb)
+                self.assertIn('quantity', pb)
+                self.assertIn('price', pb)
+                self.assertIn('price_currency', pb)
+
+        # Make sure there's no n+1 query problem
+        query_count_with_price_breaks = len(ctx)
+        query_difference = (
+            query_count_with_price_breaks - query_count_without_price_breaks
+        )
+
+        # There are 2 additional queries, 1 for the salepricebreak subselect and 1 for Currency codes because of InvenTreeCurrencySerializer
+        self.assertLessEqual(
+            query_difference,
+            2,
+            f'Query count difference too high: {query_difference} (with: {query_count_with_price_breaks}, without: {query_count_without_price_breaks})',
+        )
+
 
 class PartNotesTests(InvenTreeAPITestCase):
     """Tests for the 'notes' field (markdown field)."""